Seems that they are trying to eliminate more paid SEO stuff, and AdSense competition.
Paid Reviews Penalized by Google?
Users were also urged to remove any link back to Text-Link-Ads.com, as well as avoid adding ad disclosures such as “Sponsored Links” or “Advertisements”
http://blogoscoped.com/archive/2007-11-17-n80.html
PayPerPost Bloggers Get Slammed By Google
Google’s attempts to deny competition because PayPerPost is a “a very attractive alternative” to Adsense.
http://www.techcrunch.com/2007/11/16...med-by-google/